Trends in Charcoal Accumulation, PDSI, and Vegetation Response at Fish Lake, CA

A) Trends in charcoal accumulation (CHAR, a measure of paleofire), Palmer Drought Severity Index (PDSI, a measure of climatic conditions), and vegetation response index (VRI, a measure of forest openness) were plotted through time at Fish Lake, one of two study sites. The Little Ice Age (LIA, blue panel) and Medieval Climate Anomaly (MCA, yellow panel) indicate two time periods of known climatic changes. For example, during the MCA when climate was relatively warmer and drier, CHAR (orange line) increased, in part because forest fuels were drier and easier to burn. B) Trends in correlations between CHAR, PDSI, and VRI over time. There is a significant positive correlation between CHAR and VRI (red line) during the climatically cooler period of the Little Ice Age (600-100 years before present) as predicted by the author’s conceptual model that accounts for human-caused vegetation change through burning practices. Other correlations were found at various times throughout the record. For example, there was a significant positive correlation between CHAR and PDSI around 800 years before present. Modified from Figure 4 in (Knight et al. 2022)